The subject matter herein relates to a railway car truck and, more particularly, to a brake beam assembly for a railway car truck.
In a railway car truck, two axles are held in a pair of laterally spaced side frames, with a bolster extending laterally between and supported on each side frame. The wheels are press fit on the axles, with the ends of the axles also fitted with a roller bearing assembly. The roller bearing assembly is fit into a bearing adapter that is fit into a pedestal jaw opening at the longitudinal end of each side frame. To better control the stresses associated with heavy axle loads, the industry developed and implemented new standards for suspension systems on heavier cars. For example, heightened performance requirements have been implemented by the American Association of Railroads (AAR), such as those outlined in AAR M-976. AAR M-976 outlines the use of shear pads for the bearing adaptor. M-976 compliant railway car trucks reduce warping and side frame migration inward over time because the shear pads of the bearing adaptor provide an outward or restoring force to the side frames. However, both M-976 compliant railway car trucks and non-M-976 compliant railway car trucks are manufactured and in operation today.
Each railway car truck also includes a braking system having two brake beams that act to transmit braking force through brake shoes to the outer tread of the railway wheels. The brake beams are attached to the side frames in corresponding guide brackets having wear liners therein. For example, ends of the brake beams are received in the wear liners and are movable therein during application of the braking system.
During operation, the side frames tend to shift with respect to one another, such as when the railway car truck is going around a bend, or when the load supported by the railway car truck shifts or changes. The side frames may tend to shift inboard, which could squeeze in on the brake beam. As such, the brake beam is typically sized to create a gap or tolerance between the ends of the brake beams and the wear liners to avoid binding of the brake beams. However, such gap may be too wide in some situations, such as when the brake beam is off-center or kinked out of alignment, or when the brake beam used is undersized for the particular railway car truck. Additionally, for M-976 railway car trucks, because the shear pads of the bearing adaptor provide an outward or restoring force to the side frames, the side frames tend be separated by a greater distance than the standard or non-M-976 railway car trucks. When the gap is too wide, the brake beam is allowed to migrate within the pockets of the guide brackets and wear liners, which could lead to damage of the railcar wheels. For example, when the brake beam shifts over toward one side, the brake shoe and/or the brake head holding the brake shoe may begin to rub on the flange of the railway wheel, causing damage and/or failure of the railway wheel.
A need exists for an improved railway car truck that can compensate for conditions where the brake beam is too short or subject to being off-set.